Alloptical injection of

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All-optical injection of spin currents in
semiconductors
J.E. Sipe Department of Physics
and Institute for Optical Sciences University of
Toronto
University of Hong Kong 15 August 2005
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R.D.R. Bhat Ali Najmaie Fred Nastos Ilya
Rumyantsev Eugene Sherman
H.M. van Driel Yaser Kerachian Norman Laman
University of Toronto
A.L. Smirl Petr Nemec Martin Stevens Xinyu
Pan Hui Zhao
University of Iowa
Natural Sciences and Engineering Research
Council Photonics Research Ontario DARPA SpinS
Program

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Outline
A quick review
optical orientation
coherent current control
Two-colour phenomena
theory and experiment
One-colour phenomena
theory and experiment
Extensions and new schemes
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Outline
A quick review
optical orientation
coherent current control
Two-colour phenomena
theory and experiment
One-colour phenomena
theory and experiment
Extensions and new schemes
but first
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Some very interesting physics that WILL NOT
be important for this talk
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Some very interesting physics that WILL NOT
be important for this talk
electron-phonon interactions
electron-electron interactions
electron-hole interactions
and their spin properties
scattering from defects and
its spin properties
.
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Some very interesting physics that WILL
be important for this talk
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Some very interesting physics that WILL
be important for this talk
the presence of the lattice
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Some very interesting physics that WILL
be important for this talk
the presence of the lattice
how the electrons acquire momentum
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Some very interesting physics that WILL
be important for this talk
the presence of the lattice
how the electrons acquire momentum
spin-orbit coupling
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Some very interesting physics that WILL
be important for this talk
the presence of the lattice
how the electrons acquire momentum
spin-orbit coupling
how the spin of the electrons is coupled to
their motion
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optical orientation
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conduction
heavy hole
light hole
F. Meier and B.P. Zakharachenya, Optical
Orientation (1984)
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electrons from heavy hole band
electrons from light hole band
20 meV excess energy
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all electrons injected
20 meV excess energy
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Spin injection by two-photon absorption
R.D.R. Bhat et al., Phys. Rev. B71, 035209 (2005)
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coherent current control
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conduction
valence
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conduction
valence
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conduction
valence
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conduction
valence
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conduction
valence
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conduction
valence
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conduction
valence
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control parameter ?(2?)-2?(?)
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conduction
valence
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gasoline
energy
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gasoline
energy
road
momentum
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gasoline
energy
road
momentum
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gasoline
energy
road
momentum
photons
energy
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gasoline
energy
road
momentum
photons
energy
lattice
momentum
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gasoline
energy
road
momentum
optical motor for electrons
photons
energy
lattice
momentum
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2?(?)-?(2?)/?
A. Hache et al., Phys. Rev. Lett. 78, 306 (1997)
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can we motor up spins as well?
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two-colour phenomena
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Same circular polarizations
and
spin polarized current
direction ?? of current from crystal axis
depends on relative phase parameter ?(2?)-2?(?)
of optical fields
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injection velocity
spin polarization
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Crossed linear polarizations
no spin injection
pure spin current
magnitude of pure spin current varies as
cos (?(2?)-2?(?))
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100 meV excess energy
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spin separation d, nm (for ? 100 fs)
excess energy (meV)
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Pump-probe detection
M.J. Stevens et al. Phys. Rev. Lett. 90,
136603 (2003)
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Photoluminescence detection
Jens Hübner et al., Phys. Rev. Lett. 90, 216601
(2003)
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Battery
Spin battery
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one-colour phenomena
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injection proportional to intensity
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direction of current from crystal axis depends
on helicity of beam
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Circular photogalvanic effect
direction of current from crystal axis depends
on helicity of beam
known since the 1970s
expect current to be spin-polarized
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can be injected in wurtzite crystals
Experiment N. Laman et al. Appl. Phys. Lett.
75, 2581 (1999)
and strained zincblende crystals
Lyanda-Geller and Pikus (1989)
and GaAs quantum wells
Ganichev et al. (2001)
Golub (2004)
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Pure spin current
can be injected by a single beam even in
unstrained, bulk GaAs !
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Pure spin current
can be injected by a single beam even in
unstrained, bulk GaAs !
R.D.R. Bhat et al., Phys. Rev. Lett. 94, 096603
(2005)
300 meV excess energy
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x
y
Hui Zhao et al., submitted to Phys. Rev. Lett.
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n?
n?-n?
n?-n?
n? (arb. Units)
n?-n? (10-3, relative units)
Hui Zhao et al., submitted to Phys. Rev. Lett.
x-pump
y-pump
Probe y Position (?m)
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independent of linear polarization
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interference between circular polarized
components
independent of linear polarization
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interference between circular polarized
components
independent of linear polarization
dominates experimentally and theoretically
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Extensions and new schemes
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Quantum well geometries
unstrained
2 strain
Ali Najmaie et al., Phys. Rev. B68, 165348 (2002)
D.H. Marti et al., Phys. Rev. B69, 035335 (2004)
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Y. Kerachian et al., J. Appl. Phys. 96, 430
(2004)
New grating studies of injected currents and
spin currents
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Coherent control of exciton superpositions
1s
2p
excite a superposition...
will oscillate in time.
AC currents and AC pure spin currents !
I. Rumyantsev et al., submitted to Phys. Rev.
Lett.
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Injecting pure spin current in doped
semiconductor structures
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Injecting pure spin current in doped
semiconductor structures
use spin splitting of the conduction band
to inject pure spin current via...
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Intersubband absorption in the infrared
JETP Lett. 81, 231 (2005)
Appl. Phys. Lett. 86, 122103 (2005)
Stimulated intersubband Raman scattering in the
infrared
Phys. Rev. B72, 041304(R) (2005)
Stimulated interband Raman scattering in the
visible
Phys. Rev. Lett. 95, 056601 (2005)
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Quantum kinetics of the polar spin populations
Ilya Rumyantsev et al., in preparation
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One of the most useful men the human race has
yet produced the scientific investigator. What
actually urges him on is not some brummagem idea
of Service, but a boundless, almost pathological
thirst to penetrate the unknown, to uncover the
secret, to find out what has not been found out
before. His prototype is not the
liberator releasing slaves, the good Samaritan
lifting up the fallen, but a dog sniffing
tremendously at an infinite series of ratholes
H.L. Mencken (Reprinted in A Menchen
Crestomathy (1982))